Using the standard open source huVVer-AVI™ instrument hardware baseline, the device is preloaded with the huVVer-AVI™ Transponder Controller (TBX) firmware and connects between a compatible serial altitude encoder and a tailBeaconX™ Mode-S/ES diversity transponder. It relays the altitude information from the encoder (or a compatible EFIS device or encoding altimeter) and provides the ability to enter Squawk codes, control the transponder Modes, and provide diagnostic information.

Created for experimental aircraft applications, the huVVer-AVI Transponder Controller provides a bright 2.4 inch (61 mm) LCD screen, dual RS-232 serial ports, a sensor input for an optional external IDENT switch, and four front-panel pushbuttons. Versions are available for either 2.25” or 3.125” standard aircraft panel cutout sizes. Both 14V and 28V electrical systems are supported.


The huVVer Mk1 is available as an open source hardware design and the schematics and information can be downloaded at this page:

The huVVer-AVI Transponder Controller downloadable App is provided at


  • Provides a complete control head for the uAvionix tailBeaconX™ diversity transponder.
  • Works with existing serial altitude encoders, Electronics Flight Instrument Systems (EFIS), or encoding altimeters.
  • Supports an optional external IDENT button.
  • Software App updatable using WiFi for Over-The-Air (OTA) software upgrades.
  • Daylight Readable 850 cd/m2 320 x 240 pixel US-made color display.
  • Operates from 8 to 35 Volts DC with -20 °C to +55 °C ambient temperatures and provides extensive power and I/O conditioning to increase reliability in harsh environments


Full installation guide is located here:

For installation, you will need Mil-spec wire, a number of crimp terminals and at least one connector housing. Appropriate terminal crimper, wire cutter and wire stripper tools are also required.

  • Crimp Pins: Digikey WM2312-ND. Note: MakerPlane supplies 10 pins with each instrument.
  • Connector Housing: DigiKey WM2006-ND. Note: MakerPlane supplies two housings with each instrument.
  • Wire and wiring supplies: Mil-spec M22759/16-22 (22 AWG single), M27500/20SB1T23 (22 AWG shielded single wire), M27500/22SB2T23 (22 AWG shielded pair), plus a circuit breaker as required.

Available from Aircraft Spruce or ProWire USA.